The present invention relates to an information recording and reproducing apparatus which is designed such that a recording medium for retaining information by means of reversed magnetic domains of the magnetic recording film formed on the surface of substrate is employed, that an information is recorded by forming a reversed magnetic domain in the recording medium, and that the information is reproduced by detecting a leaky magnetic flux from the recording medium. The present invention relates also to a magnetic head to be mounted on the information recording and reproducing apparatus.
Due to the recent trend to further increase the recording density of magnetic recording disk drive, the track size of recording bit is now increasingly miniaturized. FIG. 2(a) illustrates a schematic view of a conventional magnetic reproducing head wherein a giant magneto-resistive effect (hereinafter abbreviated as GMR) film is employed as a magnetic sensor. According to this conventional magnetic reproducing head, the GMR film consisting of a laminate comprising a soft-magnetic free layer 203, a non-magnetic metallic intermediate layer 204, a ferromagnetic pinned layer 205 and an anti-ferromagnetic layer 206 for fixing the magnetization direction of the ferromagnetic pinned layer 205 is formed on an insulating film 202 which has been formed in advance on a lower shielding film 201. The GMR film thus formed is then patterned, after which permanent magnets 207 for stabilizing the magnetic properties of the GMR film and electrodes 208 for passing electric current to the GMR film are formed on both sides of this patterned GMR film. The width of track in this case is determined depending on the distance Twr between the electrodes 208.
As described in a publication, xe2x80x9cProceeding of International Symposium On Future Magnetic Storagexe2x80x9d, pages 313-319, a magnetic reproducing head employing a tunneling magneto-resistive effect (hereinafter abbreviated as TMR) film is recently attracting many attentions as an ultra-high sensitive magnetic sensor of the next generation. As shown in FIG. 2(b), this magnetic reproducing head is constructed such that a permanent magnet film 210 for stabilizing the magnetic properties of the TMR film is formed on the surface of a lower electrode 209 and then, patterned. Thereafter, the TMR film consisting of a laminate comprising a soft-magnetic free layer 211, a non-magnetic insulating intermediate layer 212, a ferromagnetic pinned layer 213 and an anti-ferromagnetic layer 214 for fixing the magnetization direction of the ferromagnetic pinned layer 213 is formed on the patterned permanent magnet film 210. Then, after an upper electrode 215 is formed on the TMR film and patterned, an insulating film 216 is formed on both sides of the TMR film. After flattening the surface of the insulating film 216, additional upper electrode 217 is formed on this flattened surface. The width of track in this case is determined depending on the width Twr between the TMR film.
FIG. 3 illustrates a schematic view of a conventional magnetic recording head. In the case of this magnetic recording head, an upper magnetic core 303 is formed via a gap film 302 on a lower magnetic core 301, wherein the lower magnetic core 301 is magnetically connected through a back contact 304 with the upper magnetic core 303. Around this back contact 304, there is disposed a coil 305 for generating a magnetic flux in a magnetic circuit constituted by the lower magnetic core 301, the back contact 304 and the upper magnetic core 303, the magnetic flux being utilized for executing the recording by means of the recording medium. In this case, the tip end 306 of the upper magnetic core 303 is narrowed as shown in FIG. 3 for the purpose of executing the recording with a narrow track width. The width of track in this case is determined depending on the width Tww of the tip end of the upper magnetic core 303.
However, if the track size is narrowed as mentioned above, there will be raised various problems that it becomes difficult to execute the patterning of the GMR film itself, and that since the influence of manufacturing error in distance between the permanent magnetic film 207 and the electrode film 208 would become proportionally enlarged, it becomes difficult to manufacture a magnetic reproducing head exhibiting a high precision in track width. Furthermore, the GMR film is now demanded to have an increasingly high sensitivity as the track size is increasingly narrowed. However, according to the aforementioned prior art, since the permanent magnets 207 are disposed on both sides of the GMR film, the magnetization is caused to be fixed on both sides of the GMR film, thereby raising the problem that the sensitivity of the GMR film to a magnetic field is deteriorated.
On the other hand, in the case of the magnetic reproducing head utilizing the TMR film as a magnetic sensor, there is the problem, in addition to the problem that the patterning of the TMR film becomes more difficult as the track size is increasingly narrowed, that since the electric resistance of the sensor is inversely proportional to the area thereof, the electric resistance of the track becomes greater as the track size is narrowed.
Even in the case of the magnetic recording head, the width Tww of the tip end of the upper magnetic core 303 is required to be narrowed still more as the track size is increasingly narrowed. However, as the track size is increasingly narrowed, the recording area of magnetic recording medium is also miniaturized, so that the demagnetization of the magnetic recording medium due to thermal demagnetization thereof becomes a serious problem now. With a view to prevent this demagnetization, measures to enhance the coercive force of magnetic recording medium are now studied. If the coercive force of magnetic recording medium is to be enhanced, a larger recording magnetic field is required to be produced. However, if it is desired to feed a large recording magnetic field from the narrowed upper magnetic core 303, it is required to make the magnetic core somewhat larger in volume. For this purpose, it is required to manufacture an upper magnetic core having a larger film thickness. However, it is difficult to precisely control the manufacturing error of the width Tww of the tip end of upper magnetic core 303.
The present invention has been made in view of the aforementioned problems of the prior art, and therefore, an object of the present invention is to provide a magnetic reproducing head and a magnetic recording head, which are easy to manufacture and suited for executing the recording and reproducing by means of magnetic recording medium of narrow track size.
Another object of the present invention is to provide a magnetic recording method and a magnetic reproducing method, which are suited for executing the recording and reproducing by means of magnetic recording medium of narrow track size.
With a view to achieve the aforementioned objects, the present inventors have developed an optical-assisted type magnetic reproducing head and an optical-assisted type magnetic recording head.
Namely, this optical-assisted type magnetic reproducing head is constituted by a GMR or TMR magnetic sensor, and a flux guide for introducing a magnetic flux into the magnetic sensor, wherein at least a portion of the flux guide is constituted by a material which is capable of permitting the magnetic flux to pass therethrough at a temperature of not lower than a predetermined temperature Tp, but not permitting the magnetic flux to pass therethrough at a temperature of lower than Tp. Furthermore, this optical-assisted type magnetic reproducing head is featured in that light is irradiated to only a portion of the flux guide to cause the temperature of the irradiated portion to rise up to Tp or more, thereby permitting a magnetic flux being fed from the magnetic recording medium to pass only through the irradiated portion, thus substantially narrowing the track width of the magnetic reproducing head on the occasion of detecting a magnetic recording information from the magnetic recording medium.
On the other hand, the optical-assisted type magnetic recording head is provided with a magnetic core, and a flux guide which is disposed to face the magnetic recording medium of the magnetic core, wherein, according to the same principle as that of the magnetic reproducing head, the temperature of the irradiated portion of the flux guide is allowed to rise up to Tp or more, thereby permitting a magnetic flux being fed from the magnetic core to pass only through the irradiated portion to the magnetic recording medium, thus substantially narrowing the track width of the magnetic recording head on the occasion of recording a magnetically reversed information in the magnetic recording medium.
It is now possible in this manner to construct a magnetic recording head and a magnetic reproducing head, which are capable of recording and reproducing information to a magnetic recording medium of small track size.
Namely, the magnetic head according to one embodiment of the present invention is featured in that it comprises a magnetic sensor for detecting a magnetic field, and a flux guide for introducing a magnetic flux into the magnetic sensor, wherein at least a portion of said flux guide is constructed to permit the magnetic flux to pass therethrough at a temperature of not lower than a predetermined temperature Tp, but not to permit the magnetic flux to pass therethrough at a temperature of lower than Tp.
Preferably, the magnetic sensor is formed of a laminate structure comprising a soft-magnetic free layer enabling the magnetization thereof to be rotated depending on an external magnetic field, a non-magnetic intermediate layer, and a ferromagnetic pinned layer where the magnetization thereof is fixed against an external magnetic field. More specifically, the magnetic sensor is formed of a giant magneto-resistive effect film (spin valve film) or a tunneling magneto-resistive effect film. These magnetic sensors are featured in that the magnetization thereof is enabled rotate depending on an external magnetic field being detected, thereby causing a relative angle thereof to the magnetization direction of the ferromagnetic pinned layer to be changed, thus producing a magneto-resistive effect.
The magnetic head according to another embodiment of the present invention is featured in that it comprises a lower magnetic core formed on a substrate, an upper magnetic core having a distal end facing the lower magnetic core with a magnetic gap film being interposed therebetween and a proximal end magnetically coupled with the lower magnetic core through a contact portion, and a coil for generating a magnetic flux in a magnetic circuit constituted by said lower magnetic core, said contact portion and said upper magnetic core, wherein a flux guide is provided at the distal end of said upper magnetic core, said flux guide being constructed to permit a magnetic flux to pass therethrough at a temperature of not lower than a predetermined temperature Tp, but not to permit the magnetic flux to pass therethrough at a temperature of lower than Tp.
The contact portion for enabling the proximal end of the upper magnetic core to be magnetically coupled with the lower magnetic core may be constructed such that the lower magnetic core is directly coupled with the upper magnetic core, or that the lower magnetic core is indirectly coupled with the upper magnetic core via a separate back contact member made of a magnetic body.
The flux guide which is capable of permitting a magnetic flux to pass therethrough at a temperature of not lower than a predetermined temperature Tp, but not permitting the magnetic flux to pass therethrough at a temperature of lower than Tp may be constituted by a material exhibiting ferromagnetic property at a temperature of not lower than the Tp and also exhibiting anti-ferromagnetic property at a temperature of lower than the Tp.
As for the materials useful for the flux guide of the magnetic head according to the present invention, it is possible to employ MnRh for instance. This MnRh is capable of exhibiting a phase transition from an anti-ferromagnetic phase to a ferromagnetic phase at a temperature of 80 degrees centigrade (Tp=80xc2x0 C.). FIG. 4 shows the temperature characteristics of the permeability of MnRh. The aforementioned portion of flux guide may not necessarily be constituted by a single layer, but may be formed of a laminate structure. Examples of 2-ply film in this case include 2-ply films consisting of NiFe and any one of materials selected from NiO, MnRh and FeMn (NiO/NiFe, MnRh/NiFe or FeMn/NiFe). As for the examples of 3-ply film, it is possible to employ NiFe/NiFeNb/CrMnPt, NiFe/NiFeNb/MnPt, etc. These 3-ply films are featured in that the permeability thereof is sharply increased at Tp=100xc2x0 C. Although not it is not specifically mentioned herein, it is of course possible to employ a 4- or more-ply film.
Preferably, the magnetic head further comprises a shading shield slit formed over the flux guide, and means for irradiating light to the flux guide through the shading shield slit.
When light is irradiated to the flux guide through the slit, it is possible to provide the flux guide with a characteristic which enables a magnetic flux to pass only through a portion thereof having a slit-like configuration where the light has been irradiated. Therefore, it is possible to form a narrowed flux pass in the magnetic head without necessitating to work the distal end portion of the flux guide or the upper magnetic core so as to make it narrower. By the way, the shading shield can be formed from a metallic film.
The flux guide may comprise an anti-ferromagnetic film which can be made from a compound selected from NiO, MnRh and FeMn.
Further, the flux guide may be constituted by a laminate film consisting of NiFe and any one of materials selected from NiO, MnRh and FeMn.
The magnetic recording and reproducing apparatus according to another embodiment of the present invention is featured in that it comprises a magnetic recording medium for retaining information by means of reversed magnetic domains, a medium-driving means for driving the magnetic recording medium, a magnetic head for executing recording and reproducing to the magnetic recording medium, and a magnetic head-driving means for driving the magnetic head relative to the magnetic recording medium, wherein said magnetic head is constituted by the aforementioned reproducing magnetic head and recording magnetic head.
The method for reproducing magnetic recording information according to another embodiment of the present invention, wherein the information is reproduced by detecting a leaky magnetic flux generated from the recording medium after the leaky magnetic flux is introduced via a flux guide into a magnetic sensor, is featured in that at least a portion of the flux guide is constituted by a material which is capable of permitting the magnetic flux to pass therethrough at a temperature of not lower than a predetermined temperature Tp, but not permitting the magnetic flux to pass therethrough at a temperature of lower than Tp; and in that light is irradiated to only a portion of the flux guide to cause the temperature of the irradiated portion to rise up to Tp or more, thereby establishing a flux pass in flux guide, the flux pass being narrower in width than that of the flux guide, thereby permitting a magnetic flux being fed from the magnetic recording medium to pass into the magnetic sensor only through the flux pass that has been established by the irradiated light.
The magnetic recording method according to another embodiment of the present invention, wherein a magnetic flux generated from a magnetic pole is applied to a magnetic recording medium to thereby execute a magnetic recording of the magnetic recording medium, is featured in that a flux guide is constituted by a material which is capable of permitting the magnetic flux to pass therethrough at a temperature of not lower than a predetermined temperature Tp, but not permitting the magnetic flux to pass therethrough at a temperature of lower than Tp; in that the flux guide is connected with a distal end of the magnetic pole; and in that light is irradiated to only a portion of the flux guide to cause the temperature of the irradiated portion to rise up to Tp or more, thereby establishing a flux pass in flux guide, the flux pass being narrower in width than that of the flux guide, thereby permitting a magnetic flux to be applied to the magnetic recording medium only through the flux pass that has been established by the irradiated light.